"Great peace have they who love your law, and nothing shall cause them to stumble" (Ps. 119:165).
"If your law had not been my delight, I would have perished in my affliction" (Ps. 119:92).
"I rejoice in your promise like one who finds great spoil" (Ps. 119:162).
The discipline of teleology is the study of the purpose or design of things and unbelievers don't like to hear that there is a purpose behind the universe or creation, but that it is just a big cosmic accident of the forces of nature. For instance, the so-called design of earth (Anthropic principle) is perfectly fit for human habitation--is that an accident?
Now, the question at hand is, why study the Bible? It should not be an academic issue or discipline to entertain us (like in a trivia game) or increase our knowledge, but to change our lives. During the Enlightenment gentlemen used to have the hobby of discussing theology, the queen of sciences, among themselves to pass the time--it was assumed everyone had a working knowledge of the Bible and could take part. Having a great knowledge of the Bible is not necessarily a compliment, because the Pharisees did too--it's what you apply That counts with God! Knowledge about the Bible is a prerequisite to knowing the Bible; it is necessary, but not sufficient to know God--the goal.
"Knowledge puffs up, but love [is what] edifies," according to 1 Cor. 8:1. But this is the kind of knowledge that doesn't contain discernment or wisdom, knowledge of God (cf. Hos. 4:1,6) "A people without discernment ["understanding" in NIV] perish" (Hos. 4:14). One of the worst sins is knowledge without character, according to Indian leader Mahatma Gandhi, because it is a fact that knowledge can be dangerous. A little knowledge is worse than none. Half-educated people are more harmful than illiterate ones.
We are not to compare or commend ourselves with others because accumulated knowledge can be a byproduct and just because someone knows a lot doesn't mean that is the goal. Knowledge is a tool for the preacher and part of his trade and he is to teach others to become independent of him and learn to fend for themselves, as it were, and someday know how to study on their own--because they love the Bible, not because they want to get smart.
You can't teach someone to love the Bible--he must practice it and apply it himself to learn this and he will learn gradually to appreciate it. He has to grow into this. One should learn to study the Bible so that he can get "Aha!" moments or epiphanies (I can remember the exact day when God opened the Scriptures to me and I couldn't stop reading them) One can then sense God is speaking to Him because this is the way God has promised to reach out to us and speak to our needs. "Study to show thyself approved unto God, a workman that needeth not to be ashamed, rightly dividing the Word of Truth" (2 Tim. 2:15, KJV).
With the privilege of interpreting Scripture, comes the responsibility to do it right and not to fabricate our own truths! The Word also "equips" us for every good work (2 Tim. 3:17)! We should all be able to say with the psalmist, "O, how I love Thy Law, it is my meditation all the day" (Ps. 119:97).
When you say something is credible because it is credible, this is not meant to be circular reasoning, like saying it's logical because logic is the only proof. It's logical to believe this because what is logical is believable. But I mean different and subtle shades of meaning. A witness's credibility must be established before he can be believed on the witness stand, and the other side seeks to destroy his credibility.
An example of circular reasoning would be to say that you think logic should be the test of Scripture because that's only logical. Actually, any standard to hold the Bible to other than itself will never stand and will break down as circular proof--the Bible must be self-attesting just as it assumes God exists and doesn't try to prove Him. The saying is, "The finite cannot grasp the infinite.